Costco Kirkland

One of the salesman at Costco was telling me about the Kirkland tires that are made for them by Michelin. The price was almost half of what they wanted for *real* Michelins. Since MAST would be the manufacturing group for these tires, how do we know that the Kirkland tires aren't made by one of the other tire companies (eg. BFG or Uniroyal)that belong to the Michelin group?